The present disclosure is directed to lifting jack assemblies which may be used on large walking machines operable for transporting massive and heavy loads, upwards of thousands of tons, over the ground. Walking machines are designed as non-wheeled, power-driven vehicles fabricated from iron and steel, and carry and sequentially transport huge structures such as oil drilling rigs and their support or service modules to pre-drilled, ground-installed conductor pipes. This may be done prior to drilling well bores in fields undergoing oil exploration, or over existing well bores in previously worked-over fields, or the like.
Walking machines generally are provided with multiple lifting jack assemblies which operate to raise and lower the apparatus and its substructure for transporting it along the ground in a straight line or steered in a selected direction. The walking machine is steered so that it is moved to align or orient equipment such as a drilling rig precisely above a well bore, or move to another area entirely. The lifting assemblies provided on known walking machines utilize lift cylinders with extendable/rods operable to raise and lower foot plates for engaging the ground, and a shifter mechanism operates to impart travel of the machine along the foot plates.